1. Field of the Invention
This invention relates to a frame-frequency converting apparatus for processing a video signal which results from 2-3 conversion of a film picture (a motion picture).
2. Description of the Prior Art
The NTSC television system has a rate of 29.97 frames (59.94 fields) per second. A standard motion picture has a rate of 24 frames per second. In general, 2-3 conversion is used to convert a motion picture into an NTSC video signal.
According to 2-3 conversion, one frame of a motion picture is changed into two successive fields related to an NTSC video signal, and a next frame of the motion picture is converted into next three successive fields related to the NTSC video signal.
Video CD's are optical disks on which moving-image information and audio information are recorded. Generally, an original video signal and an original audio signal are processed by highly-efficient encoding before being recorded on a video CD. The standards of video CD's provide a plurality of picture rates including a picture rate of 29.97 frames per second and a picture rate of 23.976 frames per second.
An NTSC video signal can be converted into a signal suited for recording on a video CD. In the case of an NTSC video signal resulting from 2-3 conversion of a motion picture, only every other field represented by the NTSC video signal is used in a signal recorded on a video CD. In this case, a video CD player reproduces two successive fields from every frame represented by the signal read out from the video CD. There periodically occur four successive fields (two successive frames) reproduced by the video CD player which originate from a same frame of the motion picture. The occurrence period agrees with a period of five frames of the motion picture. This phenomenon causes jitter in motion of images reproduced by the video CD player.